Smooth muscle is an ubiquitous tissue important to the normal function of most organs. Characteristically, the Beta-adrenergic catecholamines have relaxing effects with which a wide variety of other hormones and agonists interfere. Elucidation of the molecular mechanisms through which these interactions occur will be medically useful in confronting problems with labor, autonomic regulation in hypertension, and the gastrointestinal tract to name but a few. We have been investigating the biochemical mechanisms through which several hormones regulate uterine motility by studying their effects on the rat myometrial adenylate cyclase system, including the cAMP synthesizing enzyme itself, cAMP-dependent protein kinase, and its phosphoprotein substrates. While the Beta-adrenergic receptor was closely linked to cAMP production and smooth muscle cell relaxation in this system, the action of some hormones on uterine motility and Beta-adrenergic responsiveness was not readily explained in terms of their biochemical effects on the adenylate cyclase system. This was especially true of estrogen. In this renewal application we propose to resolve the reasons for these disparities by: determining, in greater detail, how the components of the smooth muscle adenylate cyclase system are regulated by estrogen and other steroids including the use of primary cultures of myometrial cells, and elucidating the mechanism by which a Beta-adrenergic receptor mediated yet apparently cAMP-independent event (protein kinase translocation) occurs and how it contributes to the hormonal effect. Our preliminary experiments suggest these goals can be achieved by characterization of the GTP-binding membrane protein(s) which couples the Beta-adrenergic catecholamines receptor with the adenylate cyclase catalytic subunit.